We're doing some school holidays maths. Son is 8 yo.
I don't understand the technique for this question..
these 6 numbers can be arr in 3 pairs so they add up to same answer
158 235 318 426 349 266
I've done it the hard way, but im there is a technique here.
A pair is two.
So if the sum of the units digit of a pair ends up as the same for all 3 pairs, then we might get the same sum for the 3 pairs?
The six units digits are 8, 5, 8, 6, 9, 6.
Adding any two that might give the same last number, or the sum's units digit, might solve the problem.
6+8 = 14, and 5+9 = 14.
The units digit of both sums is same 4. Umm, maybe good.
235 +349 = 584
158 +426 = 584
318 +266 = 584
Three pairs, same sum. Good.
An exercise for sudoku puzzles.
There are 6 given numbers to be divided into 3 pairs. Each pair adds up to the same number.
So, add the 6 given numbers, and divide the total by 3 to get that "same number" sum of any pair.
158 +235 +318 +426 +349 +266 = 1752
1752/3 = 584
So any pair should add up to 584.
What is the number to add to 158 to get 584?
Why, subtract 158 from 584, of course.
So, 584 - 158 = 426. Hey!
Hence one pair is 158 and 426.
Go get the other two pairs.
Okay. In 235, the last number, the 5, is the units digit.
(the first number, the 2, is the hunhreds digit; the 3 is the tens digit)
(Hundreds digit, tens digit, units digit -----for a number with 3 digits. May I assume your son understands a digit?)
So "sum of the units digits" of "235 +349" is 5+9. Which is 14. Then the units digit of this 14 is 4.
Pushing the son too early?
Is he a gifted one, though?
Advice, if your son's got a "normal" Math-brain, and he is just in 2nd Grade yet, please avoid 4th-Grade Math for now for the kid. Drill him on his current Grade level only.
If he is gifted, hey, persevere on those 4th-Grade Math exercise!
I don't think anyone has said this; forgive me if they have.
Isn't it a case of just being able to put the numbers in order? Put them in order, and then take the biggest and the smallest and pair them up. Then the next biggest and the next smallest... There is no need to do any adding or even know what the totals are.
Well they just have to be. If you're told that the numbers will pair up, then the smallest one has to go with the largest and so on. If the largest one went with anything other than the smallest, then there wouldn't be a number to go with the smallest one to make it add up.